where or how to learn to use excel very well!

Buy and read books on Excel and VBA.
View the Tips and Tutorials on this forum (and others)
Google for Excel hints, tips, tutorials, videos and examples.
Monitor this forum (and others) and observe the questions and answers. Many of the long term contributors have links to sites which provide help, examples and tutorials.
Have a burning need to produce a workbook that records, analyses and reports on data ... then ask specific questions in one of the forums (strictly speaking, fora)

It rather depends on your learning style. It can be difficult to relate to and/or apply some of the techniques if you don't have anything to work with.

Regards, TMS